In many medical procedures, such as drug delivery, it is desirable to inject a fluid into a patient. Likewise, numerous types of contrast media (often referred to simply as contrast) are injected into a patient for many diagnostic and therapeutic imaging procedures. For example, contrast media are used in diagnostic procedures such as X-ray procedures (including, for example, angiography, venography and urography), CT scanning, magnetic resonance imaging (MRI), and ultrasonic imaging. Contrast media are also used during therapeutic procedures, including, for example, angioplasty and other interventional radiological procedures. Regardless of the type of procedure, any fluid injected into the patient must be sterile and contain a minimum of pyrogens.
Typically, a fluid is injected into a patient using a manual or powered syringe. Such syringes typically comprise a reciprocally slidable plunger disposed within a cylindrical syringe body.
A number of injector-actuated syringes and powered injectors for use in angiography, computed tomography and NMR/MRI have been developed. In general, syringe plungers for use with such powered injectors require an elastomeric cover which forms a sealing engagement with the inner wall of the syringe barrel. To reduce friction and provide an adequate seal, the syringe barrel, the plunger and the elastomeric plunger cover are typically lubricated during manufacture with, for example, a silicone oil lubricant. U.S. Pat. Nos. 4,628,969 and 4,718,463 describe such lubrication.
The requirement of application of a silicone lubricant oil adds a step in the manufacturing process. Moreover, there is a risk that small amounts of silicone oil can be injected into the patient.
It is desirable to develop a syringe and a plunger for use therein in which an adequate seal is formed therebetween without the need for applying lubrication between the syringe and plunger.